FLT4-mediated ferroptosis resistance in renal cell carcinoma

Background: Renal Cell Carcinoma (RCC) is one of the ten most frequently diagnosed cancers worldwide and constitutes 2-3% of all adult cancers. Tyrosine Kinase Inhibitors (TKIs) are commonly used to treat RCC and have been shown to induce tumor cell ferroptosis, a non-apoptotic form of cell death triggered by lipid peroxidation. However, many patients develop resistance, leading to poor outcomes. FLT4, a receptor tyrosine kinase frequently deregulated in RCC, has been associated with poor survival, yet its contribution to ferroptosis resistance remains unclear. Hypothesis: We hypothesized that FLT4-driven signaling contributes to a cellular state that reduces ferroptosis sensitivity and promotes RCC progression. Methods: 1) FLT4 expression and clinical correlations were assessed using The Cancer Genome Atlas (TCGA) RCC RNAseq datasets. 2) ACHN and Caki-2 RCC cell lines were used to examine how FLT4 signaling influences proliferation, survival, stress-response pathways, lipid-associated gene expression, and ferroptosis sensitivity. 3) Luciferase- and FLT4 ovrexpressing RCC cells were implanted into NOD/SCID immunodeficient mice to evaluate tumor growth and ferroptosis-related markers in vivo. Results: FLT4 was significantly upregulated in RCC and associated with reduced patient survival. In vitro, enhanced FLT4 signaling promoted RCC cell proliferation and survival, was accompanied by reduced activity of stress-response pathways, and led to lower lipid peroxidation and decreased ferroptosis sensitivity. In vivo, FLT4 overexpression accelerated tumor growth and was associated with reduced expression of ferroptosis-related markers. Conclusion: FLT4 expression is associated with increased RCC cell growth and reduced ferroptosis sensitivity in our models. These findings describe the phenotypic consequences of altered FLT4 signaling in RCC and highlight FLT4 as a potential target for improving RCC outcomes.